Radioisotope Dating of Meteorites II: The Ordinary and Enstatite Chondrites

Abstract

Meteorites date the earth with a 4.55 ± 0.07 Ga Pb-Pb isochron called the geochron. They appear to consistently yield 4.55-4.57 Ga radioisotope ages, adding to the uniformitarians’ confidence in the radioisotope dating methods. About 82% of all meteorite falls are chondrites, stony meteorites containing chondrules. Nearly 94% of chondrites are ordinary (O) chondrites, which are subdivided into H, L, and LL chondrites based on their iron contents. Enstatite (E) chondrites comprise only 1.4% of the chondrites. Many radioisotope dating studies in the last 45 years have used the K-Ar, Ar-Ar, Rb-Sr, Sm-Nd, U-Th-Pb, Re-Os, U-Th/He, Mn-Cr, Hf-W, and I-Xe methods to yield an abundance of isochron and model ages for these meteorites from whole-rock samples, and mineral and other fractions. Such age data for fifteen O and E chondrites were tabulated and plotted on frequency versus age histogram diagrams. They generally cluster, strongly in some of these chondrites, at 4.55–4.57 Ga, dominated by Pb-Pb and U-Pb isochron and model ages, testimony to that technique’s supremacy as the uniformitarians’ ultimate, most reliable dating tool. These ages are confirmed by Ar-Ar, Rb-Sr, Re-Os, and Sm-Nd isochron ages, but there is also scatter of the U-Pb, Th-Pb, Rb-Sr, and Ar-Ar model ages, in some cases possibly due to thermal disturbance. No pattern was found in these meteorites’ isochron ages similar to the systematic patterns of isochron ages found in Precambrian rock units during the RATE project, so there is no evidence of past accelerated radioisotope decay having occurred in these chondrites. This is not as expected, because if accelerated radioisotope decay did occur on the earth, then it could be argued every atom in the universe would be similarly affected at the same time. Otherwise, asteroids and the meteorites derived from them are regarded as “primordial material” left over from the formation of the solar system, which is compatible with the Hebrew text of Genesis that could suggest God made “primordial material” on Day One of the Creation Week, from which He made the non-earth portion of the solar system on Day Four. Thus today’s measured radioisotope compositions of these O and E chondrites may reflect a geochemical signature of that “primordial material,” which included atoms of all elemental isotopes. So if some of the daughter isotopes were already in these O and E chondrites when they were formed, then the 4.55-4.57 Ga “ages” for the Richardton (H5), St. Marguerite (H4), Bardwell (L5), Bjurbole (L4), and St. Séverin (LL6) ordinary chondrite meteorites obtained by Pb-Pb and U-Pb isochron and model age dating are likely not their true real-time ages, which according to the biblical paradigm is only about 6,000 real-time years. The results of further studies of more radioisotope ages data for many more other meteorites should further elucidate these interim suggestions.

Introduction

Ever since 1956 when Claire Patterson at the California Institute of Technology in Pasadena reported a Pb-Pb isochron age of 4.55 ± 0.07 Ga for three stony and two iron meteorites, this has been declared
the age of the earth (Patterson 1956). Furthermore, many meteorites appear to have consistently dated around the same “age” (Dalrymple 1991, 2004), bolstering the evolutionary community’s confidence that
they have successfully dated the age of the earth and the solar system at around 4.57 Ga. It has also strengthened their case for the supposed reliability of the increasingly sophisticated radioisotope
dating methods.

Creationists have commented little on the radioisotope dating of meteorites, apart from acknowledging the use of Patterson’s geochron to establish the age of the earth, and that many meteorites give
a similar old age. Morris (2007) did focus on the Allende carbonaceous chondrite as an example of a well-studied meteorite analysed by many radioisotope dating methods, but he only discussed the radioisotope
dating results from one, older (1976) paper. Furthermore, he only focused on the U-Th-Pb model ages published in that paper, apparently ignoring the excellent Pb-Pb isochron age of 4.553 ± 0.004 Ga based
on some twenty isotopic analyses of the matrix, magnetic separates, aggregates and chondrules reported in that same paper, as well as the U-Pb concordia isochron age of 4.548 ± 0.025 Ga based on those
same samples.

In order to rectify this lack of engagement by the creationist community with the meteorite radioisotope dating data, Snelling (2014) obtained as much radioisotope dating data as possible for the Allende
CV3 carbonaceous chondrite meteorite (due to its claimed status as the most studied meteorite), displayed the data, and attempted to analyse it. He found that both isochron and model ages for the total
rock, separated components, or combinations of these strongly clustered around a Pb-Pb age of 4.56–4.57 Ga. However, while he then sought to discuss the possible significance of this clustering in terms
of various potential creationist models for the history of radioisotopes and their decay, drawing firm conclusions from the radioisotope dating data for just this one meteorite was premature. This present
contribution is therefore designed to document the radioisotope dating data for more meteorites, the ordinary and enstatite chondrites, so as to continue the discussion of the significance of these data.

The Classification of Meteorites

Meteorites have been classified into distinct groups and subgroups that show similar chemical, isotopic, mineral, and physical relationships. Within the evolutionary community the ultimate goal of such
a classification scheme is to group all known specimens that apparently share a common origin on a single, identifiable parent body, or even a body yet to be identified. This could be another planet,
moon, asteroid, or other current solar system object, or one that is believed to have existed in the past (for example, a shattered asteroid). However, several meteorite groups classified this way appear
to have come from a single, heterogeneous parent body, or even a single group may contain members that may have come from a variety of similar but distinct parent bodies. So any meteorite classification
system is not absolute, and is only as valid as the criteria used to develop it.

More than 24,000 meteorites are currently catalogued (Norton 2002), and this number is rapidly growing due to the ongoing discovery of large concentrations of meteorites in the world’s cold and hot deserts
(for example, in Antarctica, and Australia and Africa, respectively). Traditionally meteorites have been divided into three overall categories based on whether they are dominantly composed of rocky materials
(stones or stony meteorites), metallic material (irons or iron meteorites), or mixtures (stony-irons or stony-iron meteorites). These categories have been in use since at least the early nineteenth century,
but they are merely descriptive and do not have any genetic connotations. In reality, the term “stony-iron” is a misnomer, as the meteorites in one group (the CB chondrites) have over 50% metal by volume
and were called stony-irons until their affinities with chondrites were recognized. Similarly, some iron meteorites also contain many silicate inclusions but are rarely described as stony-irons.

Nevertheless, these three categories are still part of the most widely used meteorite classification system. Stony meteorites are traditionally divided into two other categories—chondrites (meteorites
that are characterized by containing chondrules and which apparently have undergone little change since their parent bodies originally formed), and achondrites (meteorites that appear to have had a complex
origin involving asteroidal or planetary differentiation). Iron meteorites were traditionally divided into objects with similar internal structures (octahedrites, hexahedrites, and ataxites), but these
terms are now only used for descriptive purposes and have given way to chemical group names. Stony-iron meteorites have always been divided into pallasites (which now comprise several distinct groups)
and mesosiderites (a textural term which is also synonymous with the name of a modern group).

Based on their bulk compositions and textures, meteorites have been more recently divided by Krot et al. (2005) into two major categories—chondrites and non-chondritic meteorites. They also further subdivided
the non-chondritic meteorites into the primitive achondrites and igneously differentiated meteorites, the latter including the achondrites, stony-irons (pallasites and mesosiderites), and the irons. Within
all these categories the meteorites are grouped on the basis of their oxygen isotopes, chemistry, mineralogy, and petrography.

Weisberg, McCoy and Krot (2006) made only minor changes to this classification scheme, which is illustrated in Fig. 1. Note that the three main categories have now been reduced just to chondrites, primitive
achondrites and achondrites, the main change being to simply rename the igneously differentiated meteorites the achondrites. As in Krot et al.’s (2005) classification scheme, the IAB and IIICD irons are
included in the primitive achondrites because of their silicate inclusions, while the rest of the groups of irons, the stony-irons, the martian and lunar meteorites are included with the other achondrite
groups in the achondrites.

The Chondrites

About 82% of all meteorite falls are chondrites (Norton 2002). As already noted, the chondrites derive their name from their interior texture, which is unlike any found in terrestrial rocks. Dispersed
more or less uniformly throughout these meteorites are spherical, sub-spherical and sometimes ellipsoidal structures called chondrules. These range in size from about 0.1 to 4 mm (0,0039 to 0,15 in) diameter,
with a few reaching centimeter size. Their abundance within a given chondrite can vary enormously from only a few per cent of the total volume of the meteorite to as much as 70%, with fine-grained matrix
material dispersed between the chondrules. Most chondrules are rich in the silicate minerals olivine and pyroxene. The other major components of chondrites are refractory inclusions—Ca-Al-rich inclusions
(CAIs) and amoeboid olivine aggregates (AOAs)—and Fe-Ni metal alloys and sulfides (Brearley and Jones 1998; Scott and Krot 2005; Snelling 2014).

The chondrites have been subdivided into three classes—carbonaceous (C), ordinary (O), and enstatite (E) chondrites—and fifteen groups, including the rare R and K chondrites (fig. 1). The carbonaceous
(C) chondrites, representing almost 4% of all chondrites, are so named because their matrix is carbon-rich, containing various amounts of carbon in the form of carbonates and complex organic compounds
including amino acids (Cronin, Pizzarello, and Cruikshank 1988). Further classification involves typing according to where the first meteorite or prototype in the category was found and whose characteristics
are used to define the group—for example, CI where I denotes Ivuna, a town in Tanzania, CM where M stands for Mighei in Ukraine, CV where V designates Vigarano in Italy, CO where the O stands for the
town of Ornans in France, CR where R denotes Renazzo in Italy, and CK where K designates Karoonda, a town in South Australia (Krot et al. 2009; Norton 2002).

Ordinary (O) chondrites are by far the most common type of meteorite to fall to earth. About 77% of all meteorites and nearly 94% of chondrites are ordinary chondrites. They have been divided into three
groups—H, L and LL chondrites—the letters designating their different bulk iron contents and different amounts of metal (Krot et al. 2005; Norton 2002):

H chondrites have High total iron contents and high metallic Fe (15–20% Fe-Ni alloys by mass) and smaller chondrules than L and LL chondrites. About 42% of ordinary chondrite falls belong to this
group.

L chondrites have Low total iron contents (including 7–11% Fe-Ni alloys by mass). About 46% of ordinary chondrite falls belong to this group, which makes them the most common type of meteorite to
fall to earth.

LL chondrites have Low total iron and Low metal contents (3–5% Fe-Ni alloys by mass, of which 2% is metallic Fe). About 10–12% of ordinary chondrite falls belong to this group.

Fig. 2. Two histograms showing the Mg/Si and Ca/Si compositions of chondrites (after Norton 2002; Von Michaelis, Ahrens, and Willis 1969; Van Schmus and Hayes 1974).
These atomic ratios differ significantly so that three divisions or classes of chondrites are evident—the enstatite (E) chondrites, ordinary (O) chondrites, and carbonaceous (C) chondrites. The data
even allows each class to be resolved into groups—enstatite chondrites into EH and EL; ordinary chondrites into H, L, and LL; and carbonaceous chondrites into CI, CM, CV, and CO.

Fig. 3. Plot of the weight percent oxidized iron (in minerals) versus the weight percent iron metal plus FeS (unoxidized iron) in chondrites observed to fall and recovered
shortly thereafter (after Mason 1962). A clear division of the three classes of chondrites is obvious, along with the three groups in the ordinary chondrites—H, L, and LL.

Fig. 4. Plot of the fayalite (Fa) content of olivine versus the ferrosilite (Fs) content of orthopyroxene in equilibrated ordinary chondrites clearly reveals the
existence of the three oxidation groups—H, L, and LL (after Keil and Fredriksson 1964; Norton 2002).

The E chondrites comprise only 1.4% of the chondrites, and are obviously named after their primary silicate mineral, enstatite. Enstatite is the Mg-rich end member of the orthopyroxene solid-solution
series and makes up 60–80 vol. % of these meteorites (Krot et al. 2009; Norton 2002). E chondrites contain more metal phases than any other stony meteorite class, with total iron contents varying between
22 and 33 wt %. Virtually all of their iron is in metal phases (13–28 vol. %) or as sulfides (5–17 vol. %). So like the ordinary (O) chondrites, the E chondrites are divided into two groups, EH and EL,
according to whether they have relatively High or Low total iron and metal contents. EH chondrites average about 30 vol. % total iron of which about 5 vol. % is sulfides, whereas EL chondrites have about
25 vol. % total iron with 3.5 vol. % sulfides.

Of all the meteorites, the chondrites show the greatest similarities in composition, so there are only subtle chemical differences between them. The lithophile elements (those with a strong affinity
for oxygen that tend to concentrate in silicate phases) Mg and Ca show the most distinct divisions among the chondrites. Fig. 2 provides histogram plots of Mg/Si and Ca/Si abundances in the chondrite
groups (Von Michaelis, Ahrens, and Willis 1969; Van Schmus and Hayes 1974), and shows an obvious distinction between the chondrite groups. The E chondrites exhibit the lowest element/Si ratios, while
the C chondrites cluster among the highest ratios, and the ordinary chondrites fall in a tight cluster between the two.

An even more striking distinction among the chondrites is evident when oxidized Fe is plotted against Fe in the metal phase and FeS (Mason 1962). Fig. 3 shows a clear distinction between the three classes
of chondrites. The E chondrites form a tight cluster exhibiting little oxidation, while the C chondrites display the greatest oxidation of their Fe. Again, the O chondrites fall in between, with separate
clusters for each of their constituent H, L and LL groups reflecting their respective Fe metal contents, the H chondrites having the highest Fe metal content.

The O chondrites can thus also be classified according to their range of FeO/(FeO + MgO) molecular percentages in their two most common ferromagnesian minerals, olivine and pyroxene. For meteorites in
general the fayalite (Fe2SiO4) composition of olivine most commonly lies between 15 and 30% (Fa15-30), with the olivine in a typical O chondrite in the H group having an Fa18 composition. Like olivine,
the orthopyroxene composition in meteorites is measured as the mole percent of the Fe-bearing end member, ferrosilite (FeSiO3). A typical pyroxene composition for an L group O chondrite would be Fs22.

The enstatite and three groups of ordinary chondrites are distinguished by their total iron content, both oxidized iron (combined in minerals) and metal (unoxidized iron), with the normal variations
found in the metal phase, total iron, fayalite (in olivine) and ferrosilite (in pyroxene) contents listed in Table 1. The H, L, and LL designations are as defined above, and are applied to both the O
and E chondrites. From these data in Table 1 it is evident that the more oxidized iron in minerals such as fayalite and ferrosilite, the less unoxidized iron there is as metal in the bulk composition
of these chondrite meteorites. Furthermore, as the oxidized iron increases in minerals so their oxygen content also increases. So if the mole percent fayalite (Fa) in the olivine and the mole percent
ferrosilite (Fs) in the pyroxene are plotted against each other the three ordinary chondrite groups are clearly distinguished, because the H chondrites are the least oxidized and the LL chondrites are
the most oxidized of the ordinary chondrites (fig. 4).

The classification of chondrites based on chemical and mineralogical criteria is considered a primary classification because the bulk chemistry of meteorites is a primary characteristic. However, meteorites
within a particular chemical group, such as the three groups within the ordinary (O) chondrite class, have remarkably similar bulk compositions, but under a hand lens and microscope there are striking
petrographic differences. Thus a classification system needs to take into account these petrographic differences so that meteorites can be at least roughly classified by visual inspection. This requires
secondary properties be considered, that is, properties that formed from processes which modified the original primary petrographic characteristics. Consequently, an effective classification of chondrites
takes into account both their petrographic properties and their chemical differences, using the petrographic differences to subdivide and further refine the chemical groups.

Table 1. The classification of the enstatite (E) chondrites (H, L) and ordinary (O) chondrites (H, L, LL) according to their total iron content (after Norton 2002).The symbols H, L, and LL designate the chemical abundance of iron found in each, both as metal (unoxidized) and iron combined in minerals (oxidized)—H (High total iron), L (Low total iron), and LL (Low total iron and Low iron). The fayalite content of olivine and the ferrosilite content of pyroxene are both distinguishing indicators of each group.

Class

Group

Metal
(wt %)

Total Iron
(wt %)

Fayalite
(Fa mole %)

Ferrosilite
(Fs mole %)

Enstatite

EH & EL

17–23

22–33

1

0

Ordinary

H

15–19

25–30

16–20

14–20

L

1–10

20–23

21–25

20–30

LL

1–3

19–22

26–32

32–40

Fig. 5 is a comprehensive classification chart giving ten criteria proposed by Van Schmus and Wood (1967) that with some modification is still being used to determine the petrographic type of each chondrite
group. Of the ten, most involve precise chemical and mineral analyses. However, fortunately, among the criteria (numbers 3, 4, 7, and 8) there are well-defined properties that are readily observable through
microscope study of thin sections so that the petrographic type can be visually estimated with some confidence without chemical analyses. Criteria numbers 7 and 8 are discussed here because they establish
the features needed to understand the classification of the petrographic types to which the remaining criteria refer.

Fig. 5. Chart showing the criteria for distinguishing petrographic types in chondrites (after Brearley and Jones 1998; Norton 2002; Sears and Dodd 1988; Van Schmus
and Wood 1967). The ten criteria used in this scheme as they were originally devised are displayed with the details that define each type for each criterion. The broken lines are intended to reflect
the lack of sharpness of the boundaries between two petrographic types.

Of the ten criteria, the chondrule texture and density (criterion number 7) is the most easily observed. Petrographic types range from 1 to 6. In Type 1 chondrites chondrules are absent. Type 2 chondrites
contain distinct chondrules but they are sparsely distributed within a matrix that constitutes nearly 50% of the meteorite by volume. Types 3–6 show progressive stages of thermal metamorphism. The chondrule
boundaries became progressively indistinct as solid state recrystallization occurred. This caused alteration of the original chondrule boundaries due to intergrowth of chondrules and the matrix. This
recrystallization does not represent heating to the point of fusion, but only sufficient heating to allow migration and recombination of the mineral elements into new minerals. This solid state recrystallization
occurred between 400 and 950°C.

Ordinary chondrites show petrographic types from 3 to 6 (fig. 5). Often Types 5 and 6 O chondrites show brecciated textures, composed of light clasts set against a dark matrix. It is not unusual to see
more than one petrographic type in these breccias. Typically the clasts show Type 5 or 6, while the matrix shows Type 3 or 4. In that case the entire petrographic range is designated Type 3–6. Matrix
texture (criterion number 8) is easily observed in thin sections.

Matrix textures in Type 1 and 2 chondrites are opaque (black) and very fine-grained with scattered recognizable crystal fragments. Type 2 chondrites show small chondrules, enclosing only about 12% of
the meteorites by volume. Type 3 chondrites are still unequilibrated and their matrix is still dark but chondrules are increased in number and take up 30% or more of the volume. From Type 4 to 6, increasing
thermal metamorphism in ordinary chondrites produced recrystallization of the matrix in which the crystals grew from cryptocrystalline to near naked-eye visibility. This turned the matrix transparent,
giving the interior of the chondrite a white appearance.

In examining the homogeneity of olivine and pyroxene compositions (criterion number 1) (fig. 5), from the textures of the ordinary chondrites it is assumed they all began in a relatively unmetamorphosed
state designated Type 3. The parent chondritic body from which the meteorite came is said to have been chemically unequilibrated; that is, its mineral composition was heterogeneous, showing wide variations
in chemical composition within each mineral. In particular, the two most common minerals in chondrites, olivine and pyroxene, show wide variations in their Mg/Fe compositions (table 1 and fig. 4). The
minerals in unequilibrated Type 3 O chondrites were therefore not in equilibrium with their surroundings, the iron composition in olivine and orthopyroxene varying from grain to grain by more than 5%.
This variation was progressively reduced through Type 4 until it reached nearly a singular composition at Type 5 where both have become more ferrous. All the olivine and orthopyroxene then have similar
iron compositions. Types 5 and 6 chondrites are both homogeneous and equilibrated.

The other criteria are listed in Fig. 5 and the characteristics for each criterion are provided for each petrographic type. Most are self-evident and require thin section examinations, whereas others
require mineral or bulk chemical analyses. The defining of these petrographic types adds to the classification of chondrite meteorites. The known petrographic types for the chondrite groups are summarized
in Fig. 6. Thus chemical types H, L, and LL ordinary (O) chondrites can have a petrographic type between 3 and 6, labelled as H3–H6, L3–L6, and LL3–LL6, respectively. Taken together, the carbonaceous
(C) chondrites vary from C1–6 and the enstatite (E) chondrites EH and EL 1–6.

Fig. 6. Chart summarizing the grouping of all chondrites into chemical and petrographic types (after Norton 2002). The chemical types are claimed to represent different asteroid parent bodies, while the petrographic types refer to various states of thermal metamorphism or aqueous alteration occurring on or within the parent bodies. The ordinary chondrites show thermal metamorphism, while the carbonaceous chondrites can be divided into those that show aqueous alteration and those that show thermal metamorphism. The blank boxes indicate the combinations that either do not exist or have yet to be found.

However, the exceptions are the Type 3 ordinary and carbonaceous chondrites, which have been sub-typed from 3.0 to 3.9 using a different set of criteria. This was found necessary because Type 3 ordinary
chondrites appear to have gone through an unusually large range of thermal metamorphism, more so than other types. Among the new criteria are thermoluminesence sensitivity (tendency to emit light or infrared
energy upon heating), percent matrix recrystallization, variation of cobalt in the low nickel kamacite, variations of the fayalite in olivine, and the FeO/(FeO + MgO) ratio in the matrix.

While these details are all background information, their presentation is necessary for an understanding of the identifications and designations of the meteorites investigated in this study. It is important
to establish what the different designations mean so that one can have confidence that within the groupings of the meteorites chosen for comparing their radioisotope dates the meteorites are essentially
the same chemically and mineralogically. This hopefully eliminates any differences in radioisotope ages being due to chemical and/or mineralogical differences.

The Radioisotope Dating of the Ordinary and Enstatite Chondrites

Fig. 7. Hand specimen of the L4 chondrite Bjurbole (after
Norton 2002). Its extreme friability makes it subject to
crumbling, so that the chondrules (the high relief, ovoid
shapes) frequently fall out of the surrounding matrix
leaving cavities. The specimen is 5.3 cm (2 in) in the
largest dimension.

To thoroughly investigate the radioisotope dating of the ordinary (O) and enstatite (E) chondrite meteorites all the relevant literature was searched. The objective was to find chondrites that have been
dated by more than one radioisotope method, and a convenient place to start was Dalrymple (1991, 2004), who compiled lists of such data. Ordinary (O) chondrite meteorites that were found to have been
dated multiple times by more than one radioisotope method included five H chondrites—Allegan (H5), Forest Vale (H4), Guarena (H6), Richardton (H5), and St. Marguerite (H4); three L chondrites—Bardwell
(L5), Bjurbole (L4) (fig. 7), and Bruderheim (L6) (fig. 8); and two LL chondrites—Olivenza (LL5) and St. Séverin (LL6). Five E chondrite meteorites were found to have been dated multiple times by more
than one radioisotope method—Abee (EH4), Hvittis (EL6), Indarch (EH4), St. Marks (EH5), and St. Sauveur (EH5). So this study focused on all fifteen of these meteorites. When papers containing radioisotope
dating results for these chondrites were found, the reference lists were also scanned to find further relevant papers. In this way a comprehensive set of papers, articles and abstracts on radioisotope
dating of these chondrite meteorites was collected. While it cannot be claimed that all the papers, articles and abstracts which have ever been published containing radioisotope dating results for these
chondrites have thus been obtained, the cross-checking undertaken between these publications does indicate the data set obtained is very comprehensive.

All the radioisotope dating results from these papers, articles and abstracts were then compiled and tabulated. For ease of viewing and comparing the radioisotope dating data, the isochron and model
ages for some or all components of each meteorite were tabulated separately—the H chondrites in Tables 2 (isochron ages) and 3 (model ages), the L chondrites (tables 4 and 5 respectively), the LL chondrites
(tables 6 and 7 respectively), and the E chondrites (tables 8 and 9 respectively).

Fig. 8. Photomicrograph of a cut surface of the L6
chondrite Bruderheim, which fell in Alberta, Canada,
in 1960 (after Norton 2002). The limonite (yellow-brown
hydrated iron oxides) staining of the matrix around the
included metallic iron-nickel grains demonstrates the
effect of chemical weathering after meteorites fall to
earth due to the reactions with water and atmospheric
oxygen. The horizontal field of view is 35 mm (1.3 in).

The data in these tables were then plotted on frequency versus age histogram diagrams, with the same color coding being used to show the ages obtained by the different radioisotope dating methods—the
isochron and model ages for some or all components of the H chondrites (figs. 9 and 10 respectively), of the L chondrites (figs. 11 and 12 respectively), of the LL chondrites (figs. 13 and 14 respectively),
and of the E chondrites (figs. 15 and 16 respectively).

Fig. 9. Frequency versus radioisotope ages histogram diagram for the isochron ages for some or all components of the H chondrite meteorites (a) Allegan (H5),
(b) Forest Vale (H4), (c) Guarena (H6), (d) Richardton (H5), and (e) St. Marguerite (H4), with color coding being used to show the ages obtained by the different
radioisotope dating methods. Click images for larger view.

Fig. 10. Frequency versus radioisotope ages histogram diagram for the model ages for some or all components of the H chondrite meteorites (a) Allegan (H5), (b) Forest
Vale (H4), (c) Guarena (H6), (d) Richardton (H5), and (e) St. Marguerite (H4), with color coding being used to show the ages obtained by the different radioisotope
dating methods. Click images for larger view.

Fig. 11. Frequency versus radioisotope ages histogram diagram for the isochron ages for some or all components of the L chondrite meteorites (a) Bardwell (L5), (b)
Bjurbole (L4), and (c) Bruderheim (L6), with color coding being used to show the ages obtained by the different radioisotope dating methods. Click images for larger view.

Fig. 12. Frequency versus radioisotope ages histogram diagram for the model ages for some or all components of the L chondrite meteorites (a) Bardwell (L5), (b) Bjurbole
(L4), and (c) Bruderheim (L6), with color coding being used to show the ages obtained by the different radioisotope dating methods. Click images for larger view.

Fig. 13. Frequency versus radioisotope ages histogram diagram for the isochron ages for some or all components of the LL chondrite meteorites (a) Olivenza (LL5)
and (b) St. Séverin (LL6), with color coding being used to show the ages obtained by the different radioisotope dating methods. Click images for larger view.

Fig. 14. Frequency versus radioisotope ages histogram diagram for the model ages for some or all components of the LL chondrite meteorites (a) Olivenza (LL5) and (b) St. Séverin (LL6), with color coding being used to show the ages obtained by the different radioisotope dating methods. Click images for larger view.

Fig. 15. Frequency versus radioisotope ages histogram diagram for the isochron ages for some or all components of the E chondrite meteorites (a) Abee (EH4), (b)
Hvittis (EL6), (c) Indarch (EH4), (d) St. Marks (EH5), and (e) St. Sauveur (EH5), with color coding being used to show the ages obtained by the different radioisotope dating methods. Click images for
larger view.

Fig. 16. Frequency versus radioisotope ages histogram diagram for the model ages for some or all components of the E chondrite meteorites (a) Abee (EH4), (b) Hvittis
(EL6), (c) Indarch (EH4), (d) St. Marks (EH5), and (e) St. Sauveur (EH5), with color coding being used to show the ages obtained by the different radioisotope dating
methods. Click images for larger view.

Table 2. Isochron ages for some or all components of the H chondrite meteorites Allegan (H5), Forest Vale (H4), Guarena (H6), Richardton (H5) and St. Marguerite (H4), with the details and literature
sources.

Sample

Method

Reading

Err +/-

Note

Source

Type

Allegan (H5)

whole rock samples plotted with five Barwell samples (1 each) from three other chondrite meteorites

206Pb-207Pb

4.557

0.008

Unruh, Hutchison, and Tatsumoto 1982

isochron age

feldspar, temperature extractions (800–1800°C)

I-Xe

4.573

0.003

Brazzle et al. 1999

isochron age

Forest Vale (H4)

Mn-Cr

4.5613

0.0008

Polnau and Lugmair 2000

isochron age

Mn-Cr

4.5609

0.0008

Polnau and Lugmair 2001

isochron age

Guarena (H6)

two pyroxene samples plotted with eighteen fractions of the Olivenza chondrite

Radioisotope Dating of Meteorites II: The Ordinary and Enstatite Chondrites 267 mean of a whole rock and chondrule ages of Göpel, Manhès, and Allègre (1994) and Bouvier et al (2007)

Pb-Pb

4.5644

0.0034

Kleine et al 2008

isochron age

one magnetic and three non-magnetic fractions

Hf-W

4.5653

0.0006

Kleine et al 2002

isochron age

four non-magnetic fractions and the mean of three analyses of a metal fraction

Hf-W

4.5669

0.0005

Kleine et al 2008

isochron age

internal isochron recalculated

Hf-W

4.5665

0.0005

Kleine et al 2008

isochron age

whole rock, silicate and chromite fractions

Mn-Cr

4.5649

0.0007

Polnau and Lugmair 2001

isochron age

seven fractions of minerals and chondrules

Mn-Cr

4.5629

0.001

Trinquier et al 2008

isochron age

phosphate, temperature extractions (800–1800°C)

I-Xe

4.565

0.006

Brazzle et al 1999

isochron age

feldspar, temperature extractions (800–1800°C)

I-Xe

4.567

0.002

Brazzle et al 1999

isochron age

Table 3. Model ages for some or all components of the H chondrite meteorites Allegan (H5), Forest Vale (H4), Guarena (H6), Richardton (H5), and St. Marguerite (H4), with the details and literature
sources.

Sample

Method

Reading

Err +/-

Note

Source

Type

Allegan (H5)

whole rock (with 100%, 24 out of 26 extractions)

Ar-Ar

4.511

0.011

Trieloff et al 2003

plateau age

fragments of the meteorite

206Pb-207Pb

4.5477

0.0019

Göpel, Manhès, and Allègre 1994

model age

fragments of the meteorite

206Pb-207Pb

4.5359

0.0019

Göpel, Manhès, and Allègre 1994

model age

fragments of the meteorite

206Pb-207Pb

4.5385

0.0015

Göpel, Manhès, and Allègre 1994

model age

phosphate separates

206Pb-207Pb

4.5502

0.0007

Göpel, Manhès, and Allègre 1994

model age

phosphate separates

206Pb-207Pb

4.5563

0.0008

Göpel, Manhès, and Allègre 1994

model age

Forest Vale (H4) whole rock (width 40%, 19 out of 42 extractions)

Ar-Ar

4.522

0.008

Trieloff et al 2003

plateau age

whole rock

Ar-Ar

4.52

0.03

Turner, Enright, and Hennessey 1978

plateau age

fragment of meteorite

206Pb-207Pb

4.6142

0.0042

Göpel, Manhès, and Allègre 1994

model age

phosphate separate

206Pb-207Pb

0.0007

Göpel, Manhès, and Allègre 1994

model age

Guarena (H6)

Ar-Ar

4.44

0.03

Turner, Enright, and Hennessey 1978

plateau age

whole rock (10/24 extractions, 80% Ar)

Ar-Ar

4.445

0.008

Trieloff et al 2003

plateau age

feldspar separate (9/14 extractions, 90% Ar)

Ar-Ar

4.472

0.013

Trieloff et al 2003

plateau age

pyroxene separate (9/14 extractions, 80% Ar)

Ar-Ar

4.46

0.013

Trieloff et al 2003

plateau age

mean of the whole rock, feldspar and pyroxene ages

Ar-Ar

4.454

0.006

Trieloff et al 2003

plateau age

Ar-Ar

4.44

0.06

Dalrymple 2004

plateau age

two phosphate separates

206Pb-207Pb

4.5044

0.0005

Göpel, Manhès, and Allègre 1994

model age

two phosphate separates

206Pb-207Pb

4.5044

0.0005

Göpel, Manhès, and Allègre 1994

model age

two phosphate separates

206Pb-207Pb

4.5056

0.0005

Göpel, Manhès, and Allègre 1994

model age

fragment of meteorite

206Pb-207Pb

4.5172

0.0018

Göpel, Manhès, and Allègre 1994

model age

phosphates (5)

235U-207Pb

4.538

0.004

Amelin, Ghosh, and Rotenberg 2005

isochron age

silicates (8)

235U-207Pb

4.562

0.026

Amelin, Ghosh, and Rotenberg 2005

isochron age

phosphates (5)

232Th-208Pb

4.486

0.14

Amelin, Ghosh, and Rotenberg 2005

isochron age

silicates (8)

232Th-208Pb

4.594

0.15

Amelin, Ghosh, and Rotenberg 2005

isochron age

Richardton (H5)

whole rock (width 100%, 32 out of 32 extractions)

Ar-Ar

4.595

0.011

Trieloff et al 2003

plateau age

whole rock

Ar-Ar

4.5

0.03

Turner, Enright, and Hennessey 1978

plateau age

chondrules (6) plus matrix

Rb-Sr

4.5

Evensen et al 1979

model age

chondrules (6) plus matrix

Rb-Sr

4.44

Evensen et al 1979

model age

chondrules (6) plus matrix

Rb-Sr

4.48

Evensen et al 1979

model age

chondrules (6) plus matrix

Rb-Sr

4.59

Evensen et al 1979

model age

chondrules (6) plus matrix

Rb-Sr

4.5

Evensen et al 1979

model age

chondrules (6) plus matrix

Rb-Sr

4.46

Evensen et al 1979

model age

chondrules (6) plus matrix

Rb-Sr

4.8

Evensen et al 1979

model age

mean of five phosphate fractions

Pb-Pb

4.5539

0.0028

Amelin 2000

model age

whole rock

207Pb-206Pb

4.633

Tilton 1973

model age

whole rock

207Pb-206Pb

4.604

Tilton 1973

model age

whole rock

207Pb-206Pb

4.478

0.008

Huey and Kohman 1973

model age

whole rock

207Pb-206Pb

4.519

0.015

Tatsumoto, Knight, and Allègre 1973

model age

phosphates

207Pb-206Pb

4.5514

0.0006

Göpel, Manhès, and Allègre 1994

model age

phosphates

207Pb-206Pb

4.5534

0.0006

Göpel, Manhès, and Allègre 1994

model age

plagioclase

207Pb-206Pb

4.5644

0.0064

Amelin 2001

model age

olivine

207Pb-206Pb

4.5646

0.0037

Amelin 2001

model age

pyroxene

207Pb-206Pb

4.5621

0.0009

Amelin 2001

model age

pyroxene

207Pb-206Pb

4.5627

0.001

Amelin 2001

model age

pyroxene

207Pb-206Pb

4.5649

0.0023

Amelin 2001

model age

pyroxene

207Pb-206Pb

4.5623

0.0007

Amelin 2001

model age

phosphate fractions

207Pb-206Pb

4.554

0.001

Rotenberg and Amelin 2001

model age

phosphate fractions

207Pb-206Pb

4.555

0.001

Rotenberg and Amelin 2001

model age

phosphate fractions

207Pb-206Pb

4.56

0.002

Rotenberg and Amelin 2001

model age

phosphate fractions

207Pb-206Pb

4.552

0.001

Rotenberg and Amelin 2001

model age

silicate chondrules

207Pb-206Pb

4.572

0.001

Rotenberg and Amelin 2002

model age

silicate chondrules

207Pb-206Pb

4.559

0.003

Rotenberg and Amelin 2002

model age

silicate chondrules

207Pb-206Pb

4.562

0.001

Rotenberg and Amelin 2002

model age

silicate chondrules

207Pb-206Pb

4.561

0.001

Rotenberg and Amelin 2002

model age

silicate chondrules

207Pb-206Pb

4.563

0.002

Rotenberg and Amelin 2002

model age

silicate chondrules

207Pb-206Pb

4.56

0.001

Rotenberg and Amelin 2002

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.554

0.0013

Phosphate 1

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5554

0.0007

Phosphate 2

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5531

0.0008

Phosphate 3

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5597

0.0016

Phosphate 4

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5519

0.0007

Phosphate 5

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.4593

0.005

Troilite

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5666

0.0065

Low-density fraction 1

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5638

0.0045

Low-density fraction 2

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5608

0.0261

Olivine

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5621

0.0008

Chondrule fragment 1

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5627

0.0008

Chondrule fragment 2

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5623

0.0007

Chondrule Fragment 3

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5626

0.0007

Chondrule 3

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5613

0.0008

Chondrule 4

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5608

0.001

Chondrule 8

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Tatsumoto, Knight, and Allègre 1973

207Pb-206Pb

4.5608

0.001

Chondrule 8

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5574

0.0014

Phosphate 1

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5581

0.0008

Phosphate 2

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5566

0.0008

Phosphate 3

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5705

0.0018

Phosphate 4

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.553

0.0008

Phosphate 5

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5674

0.0052

Low-density fraction 1

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5674

0.0037

Low-density fraction 2

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5864

0.0249

Olivine

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5629

0.0008

Chondrule fragment 1

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5635

0.0008

Chondrule fragment 2

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5629

0.0007

Chondrule Fragment 3

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5641

0.0007

Chondrule 3

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

207Pb-206Pb

4.5623

0.0008

Chondrule 4

Amelin, Ghosh, and Rotenberg 2005

model age

meteorite fractions and fragments using primodial Pb of Richardson troilite

Table 7. Model ages for some or all components of the LL chondrite meteorites Olivenza (LL5) and St. Séverin (LL6), with the details and literature sources.

Sample

Method

Reading

Err +/-

Note

Source

Type

Olivenza (LL5)

Ar-Ar

4.49

0.06

Turner, Enright, and Hennessey 1978

plateau age

St. Séverin (LL6)

one sample

K-Ar

4.38

0.06

Funkhouser, Kirsten, and Schaeffer 1967

model age

whole rock sample

K-Ar

4.6

0.05

used Ar-Ar measurements

Podosek 1971

plateau age

14 samples from drill core

K-Ar

4.4

0.45

used Ar-Ar measurements

Schultz and Signer 1976

plateau age

used as monitor, irradiated, stepwise-heating

Ar-Ar

4.56

0.05

Alexander, Davis, and Lewis 1972

plateau age

Ar-Ar

4.5

0.03

Podosek and Huneke 1973a

model age

weighted average calculated from three standards irradiated

Ar-Ar

4.504

0.02

Alexander and Davis 1974

model age

light and dark fractions

Ar-Ar

4.383

0.03

Hohenberg et al 1981

plateau age

Ar-Ar

4.42

0.03

plateau age

Ar-Ar

4.333

0.03

total age

Ar-Ar

4.359

0.03

total age

light fraction (Hohenberg et al 1981)

Ar-Ar

4.4313

using revised decay constants

Min, Reiners, and Shuster 2013

plateau age

Ar-Ar

4.4053

plateau age

dark fraction (Hohenberg et al 1981)

Ar-Ar

4.4688

using revised decay constants

Min, Reiners, and Shuster 2013

plateau age

Ar-Ar

4.4424

plateau age

single phosphate separate

206Pb-207Pb

4.5536

0.0007

Göpel, Manhès, and Allègre 1994

model age

206Pb-207Pb

4.5571

0.0015

model age

one whitlockite analysis only

206Pb-207Pb

4.55

0.01

Manhès, Minster, and Allègre 1978

model age

one whitlockite analysis only

208Pb-232Th

4.57

0.05

Manhès, Minster, and Allègre 1978

model age

one whitlockite analysis only

238U-206Pb

4.52

0.04

Manhès, Minster, and Allègre 1978

concordia age

235U-207Pb

4.54

0.02

concordia age

five phosphates (merrillite) grains

U-Th/He

4.412

0.075

weighted mean of five oldest grains out of fourteen analyzed

Min, Reiners, and Shuster 2013

model age

four phosphates (merrillite) grains

U-Th/He

4.152

0.07

weighted mean of four oldest grains out of five analyzed

Min, Reiners, and Shuster 2013

model age

interior whole rock sample

U-Th/He

4.1

0.15

Eugster 1988

model age

revised, anchored to ADOR

I-Xe

4.556

0.04

Glavin and Lugmair 2003

model age

Table 8. Isochron ages for some or all components of the E chondrite meteorites Abee (EH4), Hvittis (EL6), Indarch (EH4), St. Marks (EH5), and St. Sauveur (EH5), with the details and literature sources.

one whole rock samples plotted with seven other whole rock samples from three other E-chondrite meteorites

Rb-Sr

4.516

0.029

Minster, Rickard, and Allègre 1979

isochron age

one whole rock samples plotted with seven other whole rock samples from three other E-chondrite meteorites

Rb-Sr

4.508

0.037

Minster, Birck, and Allègre 1982

isochron age

one whole rock sample plotted with 16 other meteorites

207Pb-206Pb

4.505

0.008

Huey and Kohman 1973

isochron age

10 fractions from three clasts plotted with Manhès and Allègre, 1978 analyses of four meteorites

207Pb-206Pb

4.578

0.007

Bogard, Unruh, and Tatsumoto 1983

isochron age

Hvittis (EL6) 7–95% heating steps

Ar-Ar

4.547

0.006

Bogard, Dixon, and Garrison 2010

isochron age

7–95% heating steps

Ar-Ar

4.569

0.008

Bogard, Dixon, and Garrison 2010

isochron age

one whole rock sample plotted with 13 whole rock samples from other meterorites

Rb-Sr

4.54

0.13

Gopalan and Wetherill 1970

isochron age

Indarch (EH4) three whole rock samples plotted with five other whole rock samples from three other meteorites

Rb-Sr

4.516

0.029

Minster, Rickard, and Allègre 1979

isochron age

three whole rock E-chondrite samples plotted with five other E-chondrite samples

Rb-Sr

4.508

0.037

Minster, Birck, and Allègre 1982

isochron age

updated decay constant applied to Gopalan and Wetherill 1970

Rb-Sr

4.46

0.08

Dalrymple 1991

isochron age

updated with newer decay constant

Rb-Sr

4.52

0.15

Bogard, Dixon, and Garrison 2010

isochron age

updated with newer decay constant

Rb-Sr

4.449

0.043

Bogard, Dixon, and Garrison 2010

isochron age

updated with newer decay constant

Rb-Sr

4.5

0.13

Bogard, Dixon, and Garrison 2010

isochron age

St. Marks (EH5) two whole rock samples plotted with 12 other whole rock samples of seven other meteorites

Rb-Sr

4.54

0.13

Goplan and Wetherill 1970

isochron age

three whole rock samples plotted with five other whole rock samples from three other E-chondrite meteorites

Rb-Sr

4.516

0.029

Minster, Rickard,and Allègre 1979

isochron age

nine fractions of whole rock

Rb-Sr

4.335

0.05

Minster, Rickard, and Allègre 1979

isochron age

three whole rock samples plotted with five other whole rock samples from three other E-chondrite meteorites

Rb-Sr

4.508

0.037

Minster, Birck, and Allègre 1982

isochron age

updated with newer decay constant

Rb-Sr

4.391

0.05

Bogard, Dixon, and Garrison 2010

isochron age

St. Sauveur (EH5)

one whole rock sample plotted with seven other whole rock samples from three other E-chondrite meteorites

Rb-Sr

4.516

0.029

Minster, Rickard, and Allègre 1979

isochron age

nine fractions of whole rock

Rb-Sr

4.457

0.047

Minster, Rickard, and Allègre 1979

isochron age

one whole rock sample plotted with seven other whole rock samples from three other E-chondrite meteorites

Rb-Sr

4.508

0.037

Minster et al 1982

isochron age

updated with newer decay constant

Rb-Sr

4.514

0.047

Bogard, Dixon, and Garrison 2010

isochron age

one whole rock sample plotted with three other E-chondrite meteorites

207Pb-206Pb

4.577

0.004

Manhès and Allègre 1978

isochron age

Table 9. Model ages for some or all components of the E chondrite meteorites Abee (EH4), Hvittis (EL6), Indarch (EH4), St. Marks (EH5), and St. Sauveur (EH5), with the details and literature sources.

Sample

Method

Reading

Err +/-

Note

Source

Type

Abee (EH4)

Clast 1, 1, 04

Ar-Ar

4.5

0.03

Bogard, Unruh, and Tatsumoto 1983

plateau age

Clast 2, 2, 05

Ar-Ar

4.52

0.03

Bogard, Unruh, and Tatsumoto 1983

plateau age

Clast 3, 3, 06

Ar-Ar

4.49

0.03

Bogard, Unruh, and Tatsumoto 1983

plateau age

Clast 1, 1, 04 (350°C)

Ar-Ar

4.1

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (450°C)

Ar-Ar

4.43

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (525°C)

Ar-Ar

4.5

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (600°C)

Ar-Ar

4.38

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (650°C)

Ar-Ar

4.41

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (725°C)

Ar-Ar

4.52

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (800°C)

Ar-Ar

4.5

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (875°C)

Ar-Ar

4.53

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (975°C)

Ar-Ar

4.48

0.03

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (1090°C)

Ar-Ar

4.39

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (1250°C)

Ar-Ar

4.13

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (1400°C)

Ar-Ar

3.63

0.06

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 04 (1500°C)

Ar-Ar

3.56

0.06

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (300°C)

Ar-Ar

7.2

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (400°C)

Ar-Ar

4.8

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (500°C)

Ar-Ar

4.33

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (600°C)

Ar-Ar

4.5

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (675°C)

Ar-Ar

4.52

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (750°C)

Ar-Ar

4.52

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (800°C)

Ar-Ar

4.54

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (900°C)

Ar-Ar

4.5

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (1000°C)

Ar-Ar

4.43

0.03

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (1150°C)

Ar-Ar

4.27

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (1300°C)

Ar-Ar

4.03

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 2, 2, 05 (1550°C)

Ar-Ar

3.99

0.09

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (300°C)

Ar-Ar

8.9

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (400°C)

Ar-Ar

5.4

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (500°C)

Ar-Ar

3.82

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (600°C)

Ar-Ar

4.15

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (675°C)

Ar-Ar

4.31

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (725°C)

Ar-Ar

4.38

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (775°C)

Ar-Ar

4.47

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (850°C)

Ar-Ar

4.49

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (950°C)

Ar-Ar

4.39

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (1050°C)

Ar-Ar

4.29

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (1175°C)

Ar-Ar

4

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (1325°C)

Ar-Ar

3.76

0.02

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 3, 3, 06 (1500°C)

Ar-Ar

3.58

0.09

Bogard, Unruh, and Tatsumoto 1983

step-heating age

Clast 1, 1, 01; fraction 1, 1, I

207Pb-208Pb

4.56

0.15

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 1, 1, 01; fraction 1, 1, E1

207Pb-208Pb

4.72

0.05

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 1, 1, 01; fraction 1, 1, E2

207Pb-208Pb

4.56

0.1

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 1, 1, 01; fraction 1, 1, E2 (H2O-L)

207Pb-208Pb

4.45

0.07

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 2, 2, 02; fraction 2, 2, I

207Pb-208Pb

4.7

0.1

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 2, 2, 02; fraction 2, 2, E

207Pb-208Pb

4.54

0.13

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 2, 2, 02; fraction 2, 2, E (H2O-L)

207Pb-208Pb

4.41

0.03

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 3, 3, 07; fraction 3, 3, I

207Pb-208Pb

4.56

0.1

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 3, 3, 07; fraction 3, 3, E

207Pb-208Pb

4.7

0.06

Bogard, Unruh, and Tatsumoto 1983

model age

Clast 3, 3, 07; fraction 3, 3, E (H2O-L)

207Pb-208Pb

4.55

0.05

Bogard, Unruh, and Tatsumoto 1983

model age

Hvittis (EL6)

clast (whole rock)

Ar-Ar

4.47

Kinsey et al 1995

plateau age

Ar-Ar

4.544

0.018

Bogard, Dixon, and Garrison 2010

plateau age

7-95% heating steps

Ar-Ar

4.494

0.046

Bogard, Dixon, and Garrison 2010

plateau age

250°C

Ar-Ar

4.2276

0.0131

Bogard, Dixon, and Garrison 2010

model (step heating) age

300°C

Ar-Ar

3.7347

0.0078

Bogard, Dixon, and Garrison 2010

model (step heating) age

350°C

Ar-Ar

3.6969

0.0054

Bogard, Dixon, and Garrison 2010

model (step heating) age

400°C

Ar-Ar

3.9411

0.0057

Bogard, Dixon, and Garrison 2010

model (step heating) age

475°C

Ar-Ar

4.2912

0.0049

Bogard, Dixon, and Garrison 2010

model (step heating) age

550°C

Ar-Ar

4.5024

0.0049

Bogard, Dixon, and Garrison 2010

model (step heating) age

600°C

Ar-Ar

4.5285

0.0048

Bogard, Dixon, and Garrison 2010

model (step heating) age

650°C

Ar-Ar

4.5295

0.0047

Bogard, Dixon, and Garrison 2010

model (step heating) age

700°C

Ar-Ar

4.5457

0.0044

Bogard, Dixon, and Garrison 2010

model (step heating) age

725°C

Ar-Ar

4.5535

0.0045

Bogard, Dixon, and Garrison 2010

model (step heating) age

750°C

Ar-Ar

4.5606

0.0044

Bogard, Dixon, and Garrison 2010

model (step heating) age

775°C

Ar-Ar

4.56

0.0046

Bogard, Dixon, and Garrison 2010

model (step heating) age

825°C

Ar-Ar

4.5557

0.0045

Bogard, Dixon, and Garrison 2010

model (step heating) age

875°C

Ar-Ar

4.5393

0.0046

Bogard, Dixon, and Garrison 2010

model (step heating) age

925°C

Ar-Ar

4.5112

0.0046

Bogard, Dixon, and Garrison 2010

model (step heating) age

975°C

Ar-Ar

4.4783

0.0052

Bogard, Dixon, and Garrison 2010

model (step heating) age

1025°C

Ar-Ar

4.4222

0.005

Bogard, Dixon, and Garrison 2010

model (step heating) age

1100°C

Ar-Ar

4.4498

0.0045

Bogard, Dixon, and Garrison 2010

model (step heating) age

1200°C

Ar-Ar

4.4444

0.0043

Bogard, Dixon, and Garrison 2010

model (step heating) age

1300°C

Ar-Ar

4.1384

0.0047

Bogard, Dixon, and Garrison 2010

model (step heating) age

1400°C

Ar-Ar

4.4291

0.0283

Bogard, Dixon, and Garrison 2010

model (step heating) age

Indarch (EH4)

29-83% five extractions

Ar-Ar

4.249

0.013

Bogard, Dixon, and Garrison 2010

model (plateau) age

83–99% extractions

Ar-Ar

4.351

0.008

Bogard, Dixon, and Garrison 2010

model (plateau) age

525°C

Ar-Ar

3.8659

0.0059

Bogard, Dixon, and Garrison 2010

model (step heating) age

625°C

Ar-Ar

4.0582

0.005

Bogard, Dixon, and Garrison 2010

model (step heating) age

700°C

Ar-Ar

4.1812

0.0044

Bogard, Dixon, and Garrison 2010

model (step heating) age

775°C

Ar-Ar

4.2169

0.0036

Bogard, Dixon, and Garrison 2010

model (step heating) age

825°C

Ar-Ar

4.255

0.004

Bogard, Dixon, and Garrison 2010

model (step heating) age

875°C

Ar-Ar

4.2538

0.0048

Bogard, Dixon, and Garrison 2010

model (step heating) age

925°C

Ar-Ar

4.2492

0.0038

Bogard, Dixon, and Garrison 2010

model (step heating) age

975°C

Ar-Ar

4.2275

0.0038

Bogard, Dixon, and Garrison 2010

model (step heating) age

1075°C

Ar-Ar

4.2525

0.0035

Bogard, Dixon, and Garrison 2010

model (step heating) age

1125°C

Ar-Ar

4.2977

0.0037

Bogard, Dixon, and Garrison 2010

model (step heating) age

1225°C

Ar-Ar

4.2958

0.0048

Bogard, Dixon, and Garrison 2010

model (step heating) age

1325°C

Ar-Ar

4.3511

0.0073

Bogard, Dixon, and Garrison 2010

model (step heating) age

1450°C

Ar-Ar

4.1725

0.0149

Bogard, Dixon, and Garrison 2010

model (step heating) age

whole rock

K-Ar

4.2

0.1

Schaeffer and Stoenner 1965

model age

enstatite

K-Ar

4.45

0.16

Schaeffer and Stoenner 1965

model age

relative to Shallowater

I-Xe

4.56

Busfield, Turner, and Gilmour 2008

model age

St. Marks (EH5) 71–91% extraction

Ar-Ar

4.433

0.004

Bogard, Dixon, and Garrison 2010

model (maximum) age

59–71% extraction

Ar-Ar

4.411

0.005

Bogard, Dixon, and Garrison 2010

model (maximum) age

950°C

Ar-Ar

3.7429

0.0103

Bogard, Dixon, and Garrison 2010

model (step heating) age

1050°C

Ar-Ar

4.0609

0.0051

Bogard, Dixon, and Garrison 2010

model (step heating) age

1125°C

Ar-Ar

4.2363

0.004

Bogard, Dixon, and Garrison 2010

model (step heating) age

1200°C

Ar-Ar

4.236

0.0058

Bogard, Dixon, and Garrison 2010

model (step heating) age

1275°C

Ar-Ar

4.3382

0.0039

Bogard, Dixon, and Garrison 2010

model (step heating) age

1325°C

Ar-Ar

4.4107

0.004

Bogard, Dixon, and Garrison 2010

model (step heating) age

1375°C

Ar-Ar

4.4329

0.0031

Bogard, Dixon, and Garrison 2010

model (step heating) age

1450°C

Ar-Ar

4.3504

0.0066

Bogard, Dixon, and Garrison 2010

model (step heating) age

1600°C

Ar-Ar

4.1247

0.0666

Bogard, Dixon, and Garrison 2010

model (step heating) age

relative to Shallowater

I-Xe

4.56

Busfield, Turner, and Gilmour 2008

model age

St. Sauveur (EH5)

relative to Shallowater

I-Xe

4.56

Busfield, Turner, and Gilmour 2008

model age

Discussion

In contrast to the Allende CV3 carbonaceous chondrite meteorite (Snelling 2014), there have been fewer radioisotope methods used on these meteorites and therefore fewer radioisotope ages obtained. However,
even a cursory examination of Figs. 9–16 reveals that there is still a clustering of radioisotope ages, both isochron and model ages, around 4.55–4.57 Ga. And where there are larger numbers of radioisotope
ages available the clustering around 4.55–4.57 Ga is very pronounced, similar to the pattern found for Allende CV3 carbonaceous chondrite by Snelling (2014). Again this clustering is dominated by Pb-Pb
isochron and model ages, and Pb-Pb calibrated Mn-Cr, Hf-W, and I-Xe ages, but it is also supported by some U-Pb, Th-Pb, Rb-Sr, Sm-Nd, Ar-Ar, and Re-Os ages. There is also much scattering of K-Ar, Ar-Ar,
Rb-Sr, Sm-Nd, U-Pb, Th- Pb, Re-Os, and U-Th/He ages, though the pattern varies from meteorite to meteorite and depends on which methods were applied to them.

The H Chondrites

The Richardton (H5) meteorite has been the most radioisotope dated of the H chondrites, and the clustering of both its Pb-Pb isochron and model ages at 4.55–4.57 Ga is very strong (figs 9 and 10). St.
Marguerite (H4) has only Pb-Pb isochron ages that are around 4.56–4.57 Ga. As to be expected, by definition the Mn-Cr and Hf-W isochron ages coincide with the St. Marguerite’s Pb-Pb isochron ages because
they have been calibrated against the St. Marguerite meteorite’s Pb-Pb isochron and model ages (figs. 9 and 10) (Göpel, Manhès, and Allègre 1994; Polnau and Lugmair 2001; Kleine et al. 2002, 2008; Trinquier
et al. 2008), and the I-Xe isochron ages similarly coincide with the Pb-Pb isochron ages (fig. 9), because they are calibrated against the I-Xe isochron age of the Shallowater achondrite, which in turn
is calibrated against the Pb-Pb ages of several other meteorites (Brazzle et al. 1999; Gilmour et al. 2006, 2009). Thus the Richardton (H5) meteorite’s Mn-Cr, Hf-W, and I-Xe isochron ages also coincide
with its Pb-Pb isochron ages at 4.56–4.57 Ga for the same reasons. But Richardton’s Pb-Pb isochron and model 4.56–4.57 Ga ages are both supported by U-Pb isochron and model ages and a Th-Pb model age
(figs. 9 and 10). Nevertheless, there is also some scatter of U-Pb, Th-Pb, Sm-Nd, and Rb-Sr isochron ages for Richardton (H5) either side of this strong 4.56–4.57 Ga clustering, plus two outlying Rb-Sr
isochron ages and one outlying Sm-Nd isochron age (table 2 and fig. 9). In contrast, there is considerable wide scatter of U-Pb, Th-Pb, Ar-Ar, and Rb-Sr model ages for Richardton (H5) (table 3 and fig.
10). And there is no real pattern to this scatter. For both isochron and model ages there are U-Pb, Th-Pb, Rb-Sr, Sm-Nd, and Ar-Ar ages respectively either side of the strong 4.56–4.57 Ga clustering,
although the U-Pb isochron ages are all lower (younger) than the clustering, while the U-Pb model ages are nearly all above (older) than the clustering. Furthermore, when the U-Pb and Th-Pb model ages for the same sample fractions in the same study are compared [for example, the Amelin, Ghosh, and Rotenberg (2005) data in table 3], the U-Pb model ages are for some sample fractions older than the Th-Pb
model ages, and for other sample fractions younger than the Th-Pb model ages.

The other three H chondrites in tables 2 and 3, and figs. 9 and 10, have only a few radioisotope age data for them. Allegan (H5) has one Pb-Pb 4.56 Ga isochron age, one I-Xe isochron age (which via calibration
agrees with the Pb-Pb isochron age) and two Pb-Pb 4.56 Ga model ages. Forest Vale (H4) has only two Mn-Cr isochron ages that are calibrated by St. Marguerite’s Pb-Pb isochron age (Polnau and Lugmair 2000,
2001), so by definition there is agreement. In contrast, the Guarena (H6) meteorite only has one Sm-Nd isochron age which is older than 4.56–4.57 Ga, whereas the four Rb-Sr isochron ages are scattered,
with one at 4.56 Ga, one above 4.56 Ga, and two below 4.50 Ga. Among the model ages for these three H chondrites, the Ar-Ar model ages are all younger than their corresponding Pb-Pb-Pb model ages (fig.
10). However, whereas one Pb-Pb model age for Forest Vale (H4) is older than the other 4.56 Ga Pb-Pb model age, all four Pb-Pb model ages for Guarena (H6) are younger than the 4.56–4.57 Ga “target,” and
all six Ar-Ar model ages are much younger. This could well be related to the classification of these meteorites on a scale of increasing thermal metamorphism from H4 through to H6 (fig. 6) based on the
observable and measurable criteria listed in fig. 5 (Norton 2002; Van Schmus and Wood 1967). It is thus logical that the U-Pb and K-Ar systems in the more thermally metamorphosed (to higher temperatures)
Guarena (H6) meteorite have been disturbed, some of the daughter Ar gas particularly having been lost and thus resulting in younger Ar-Ar measured ages.

The L Chondrites

All three meteorites investigated have only a few isochron and model ages via only a few radioisotope dating methods (tables 4 and 5, and figs. 11 and 12). However, the clustering of the radioisotope
ages is again around the 4.55–4.57 Ga mark. This “target” date was achieved by both Pb-Pb and U-Pb isochron ages for Bardwell (L5) and Bjurböle (L4), and by both Pb-Pb and U-Pb model ages for Bardwell
(L5), but only by Pb-Pb model ages for Bjurböle (L4). One Rb-Sr, one I-Xe, and two Sm-Nd isochron ages also cluster around the 4.55–4.57 Ga mark for Bjurböle (L4), but one Rb-Sr isochron age is slightly
younger and one Sm-Nd isochron age is very much younger. The I-Xe isochron age, though initially designated as the I-Xe standard (Hohenberg and Kennedy 1981), by definition agrees with Bjurböle’s Pb-Pb
isochron age, because its I-Xe isochron age has also been calibrated against the I-Xe isochron age of the Shallowater achondrite, which in turn is calibrated against the Pb-Pb ages of several other meteorites
(Brazzle et al. 1999; Gilmour et al. 2006, 2009). The other patterns are that for both Bardwell (L5) and Bjurböle (L4) the K-Ar and Ar-Ar model ages are consistently younger than the “target” age, while
one Pb-Pb model age for each meteorite is well above (much older) than the 4.55–4.57 Ga cluster.

The sole U-Th/He model age for Bjurböle (L4), similar to its K-Ar and Ar-Ar model ages, is much younger than the 4.55–4.57 Ga mark (fig. 12), probably because these methods depend on daughter isotopes
He and Ar that are noble (inert) gases of light atomic weights and small sizes which therefore are prone to diffusing away from their parent radioisotopes and escaping completely from the host mineral
lattices. Indeed, it has been suggested that severe heating after meteorite formation may cause total loss of both gases, which results in the He and Ar ages being younger and concordant, with both clocks
reset to zero at the time of the heating event after the meteorites formed (Lewis 1997). Furthermore, where U-Th/He ages are younger than K-Ar and Ar-Ar ages, as here for the Bjurböle (L4) chondrite (fig.
12), it has been suggested that even moderate heating of the meteorites would have caused He to diffuse out of the mineral grains in a time too short for major loss of the more slowly diffusing Ar.

As a more thermally metamorphosed meteorite, Bruderheim (L6) displays a slightly different pattern, consistent with disturbance of the radioisotope systems. Among the few isochron ages it is the two
U-Pb and single Rb-Sr isochron ages that cluster around the 4.55–4.57 Ga mark, while the single Pb-Pb isochron age is less than 4.50 Ga (fig. 11). However, among the model ages it is the Pb-Pb model ages
that cluster close to and just below the 4.55–4.57 Ga mark, while the U-Pb model ages are widely scattered both well above (older) and well below (younger), and around the 4.55–4.57 Ga mark.

The LL Chondrites

Only two LL chondrites have been radioisotope dated multiple times. For the Olivenza (LL5) meteorite only Rb-Sr isochron and Ar-Ar model ages have been obtained (figs. 13 and 14), and these are somewhat
scattered with respect to the 4.55–4.57 Ga mark, with one Rb-Sr isochron age above and the other ages below. In contrast, the St. Séverin (LL6) meteorite’s age has been well constrained by one Rb-Sr,
one Re-Os, three Pb-Pb, and one Sm-Nd 4.56–4.57 Ga isochron ages (fig. 13), and by three Pb-Pb, one Th-Pb, and one Ar-Ar 4.56–4.57 Ga model ages (fig. 14). These 4.56–4.57 Ga ages are also supported by
Mn-Cr isochron and I-Xe isochron and model ages, as is to be expected because of these methods being calibrated against Pb-Pb isochron and model ages for other meteorites (Brazzle et al. 1999; Gilmour
et al. 2006, 2009; Kleine et al. 2008; Polnau and Lugmair 2001; Trinquier et al. 2008). Again there is also scatter, with Re-Os, Rb-Sr, and Pb-Pb isochron ages above the 4.56–4.57 Ga mark, and Rb-Sr and
Pb-Pb isochron ages below. In contrast, apart from one K-Ar model age above the 4.56–4.57 Ga mark (table 7), all the other K-Ar and Ar-Ar (bar one) model ages, and the U-Pb and U-Th/He model ages, are
below the 4.56–4.57 Ga mark. In fact, many of the Ar-Ar, K-Ar, and U-Th/He model ages are well below the 4.56–4.57 Ga mark (table 7), with a clustering of such model ages centred around the 4.00–4.20
Ga mark. Two U-Th/He ages are lower outliers. The probable explanation for this pattern would seem to be that these methods depend on daughter isotopes that are noble (inert) gases of light atomic weights
and small sizes which therefore are prone to diffusing away from their parent radioisotopes and escaping completely from the host mineral lattices, especially due to a heating event subsequent to meteorite
formation (Lewis 1997). Conventionally this 4.00–4.20 Ga age clustering would be identified as the age of such a re-heating event that reset the K-Ar, Ar-Ar, and U-Th/He model ages due to the loss of
Ar and He gases (Bogard 2011; Min, Reiners, and Shuster 2013; Trieloff et al. 2003).

The E Chondrites

Five E chondrites have been dated by more than one radioisotope method—four by the Rb-Sr and Pb-Pb isochron methods and one by the Ar-Ar and Rb-Sr isochron methods (fig. 15); two by the Ar-Ar and Pb-Pb
model age methods, two by the K-Ar, Ar-Ar, and I-Xe model age methods, and one just by the I-Xe model age method (fig. 16). None of the methods produced results on these meteorites that clustered at the
4.56–4.57 Ga mark, except for the I-Xe model ages for Indarch (EH4), St. Marks (EH5), and St. Sauveur (EH5). These are by definition in agreement with this 4.56–4.57 age, because I-Xe ages are always
calibrated against the I-Xe age of the Shallowater achondrite (Busfield, Turner, and Gilmour 2008), which in turn is calibrated against the Pb-Pb ages of several other meteorites that date at the 4.56–4.57
Ga mark (Brazzle et al. 1999; Gilmour et al. 2006, 2009). However, some individual age determinations did produce results in the 4.56–4.57 Ga range—one Ar-Ar isochron age for Hvittis (EL6), one Rb-Sr
isochron age for Indarch (EH4), and one Pb-Pb isochron age for St. Sauveur (EH5) (fig.15); four Pb-Pb model ages for Abee (EH4), and four Ar-Ar model ages for Hvittis (EL6) (fig.16).

Otherwise, in general the Rb-Sr isochron ages for these meteorites are younger than the 4.56–4.57 Ga “target” age (except for the one Rb-Sr isochron age for Indarch that is in that range), and younger
than or equal to all of both the Pb-Pb and Ar-Ar isochron ages, the one exception being an Abee (EH4) Pb-Pb isochron age (fig. 15). This pattern of isochron ages for these two β-decaying radioisotope
systems is not consistent with that reported by the RATE project, which found that K-Ar and Ar-Ar isochron ages were always younger than Rb-Sr isochron ages (Snelling 2005; Vardiman, Snelling and Chaffin
2005). Among the model ages the Ar-Ar (and the two K-Ar) model ages are widely scattered and invariably are younger than both the 4.55–4.57 Ga target age and the Pb-Pb model ages, except for the four
Hvittis (EL6) Ar-Ar ages in the 4.55–4.57 Ga range, and the four Abee (EH4) Ar-Ar model ages greater than 4.8 Ga (fig. 16). Both the K-Ar and Pb-Pb systems seem to have been affected in the Abee (EH4)
meteorite, as the Pb-Pb model ages are scattered between 4.42 and 4.72 Ga (table 9), which is much less that the scatter in the Ar-Ar model ages between 3.56 and 8.9 Ga. The usual explanation for disturbance
of the K-Ar (and Ar-Ar) system is a heating event sometime after formation of the meteorite’s parent body (Bogard 2011; Min, Reiners, and Shuster 2013; Trieloff et al. 2003), so that might explain this
pattern in these E chondrites. The U-Pb system if usually perturbed by earth surface weathering, so perhaps the Abee (EH4) chondrite was affected by water on the earth’s surface before it was recovered
for study.

Comparisons to the RATE Study

One of the issues Snelling (2014) discussed in relation to the radioisotope ages that have been obtained for the Allende CV3 carbonaceous chondrite is whether the meteorite yielded a pattern of isochron
ages similar to that found for earth rocks by the 1997–2005 RATE (radioisotopes and the age of the earth) project (Vardiman, Snelling, and Chaffin 2005). The major conclusion of the RATE project was that
radioisotope decay rates have not necessarily been constant throughout earth history, because there is evidence that there have been one or more episodes of accelerated rates of radioisotope decay, particularly
during the Flood only about 4350 years ago (Vardiman, Snelling, and Chaffin 2005). While there were several lines of documented evidence that confirmed this conclusion, the principal evidence was different
isochron ages obtained from the same samples from the same rock units by the different radioisotope dating methods (Snelling 2005; Vardiman, Snelling, and Chaffin 2005). Furthermore, there was a consistent
pattern to the isochron ages from the different methods that indicated that there was an underlying systematic cause of these age differences, namely, an episode (or episodes) of accelerated radioisotope
decay (Snelling 2005; Vardiman, Snelling, and Chaffin 2005). For example, it was found that the α-decaying radioisotopes U and Sm always gave older ages than the β-decaying K and Rb. And then between
the β-decayers, K with the shorter half-life (more rapid decay today) and the lighter atomic weight, always yielded younger ages than the slower decaying and heavier Rb. While exactly the same pattern
was not confirmed among the α-decaying U and Sm radioisotopes, both their half-lives and atomic weights were still believed to be the factors at work.

The mechanism proposed for this past episode (or episodes) of accelerated radioisotope decay was small changes to the binding forces in the nuclei of the parent radioisotopes (Vardiman, Snelling, and
Chaffin 2005). These changes would thus have to have affected every atom making up the earth, and by logical extension every atom of the universe at the same time, because God appears to have created
the physical laws governing the universe to operate consistently through time and space, though of course He Himself is not bound by those physical laws which He can change at any time anywhere or everywhere.
Therefore, we should expect that this past episode(s) of accelerated radioisotope decay had affected the asteroids from where many meteorites have come, and that the meteorites may thus today yield the
same pattern of different radioisotope ages from the different radioisotope dating methods.

Snelling (2014) found no pattern of isochron ages similar to the patterns found in the RATE study was yielded by the Allende CV3 carbonaceous chondrite, and the same is true of the isochron ages for
the fifteen H, L, LL, and E chondrites reported in this study, as already discussed above. In fact, the β-decay isochron ages (Rb-Sr, Re-Os) are sometimes older than the α-decay (U, Sm) isochron ages.
Furthermore, the E chondrites yielded Rb-Sr isochron ages generally younger than or equal to their Ar-Ar isochron ages (table 8 and fig. 15), when the pattern in the RATE study’s rocks was the opposite
because Rb has a longer half-life and a heavier atomic weight. In contrast, the Re-Os isochron ages yielded by the St. Séverin (LL6) chondrite were greater than or equal to its Rb-Sr isochron ages (table
6 and fig. 13). While the RATE study didn’t deal with Re-Os isochron ages, this pattern is arguably somewhat predictable from the conclusions of the RATE study, because while the β-decaying Re has a slightly
shorter half-life (at 42.7 billion years) than the β-decaying Rb (at 48.8 billion years), it has a heavier atomic weight (187 for Re compared to 87 for Rb) (Faure and Mensing 2005). So if the atomic weight
is the dominant factor in the amount of accelerated radioisotope decay which occurred, then the Re-Os isochron ages should be older than the Rb-Sr isochron ages, though the effect of the half-lives may
result in the occasional equality of their isochron ages.

Extending this argument further, if the atomic weight is the dominant factor in the amount of accelerated radioisotope decay which occurred, then among the α-decaying parent radioisotopes the Pb-Pb isochron
ages should be older than the Sm-Nd isochron ages, because the parent U radioisotopes have atomic weights of 238 and 235, whereas the parent Sm radioisotope’s atomic weight is only 147. But again the
heavier atomic weight U radioisotopes have shorter half-lives (at 4.47 billion years and 0.704 billion years respectively) than Sm (at 106 billion years) (Faure and Mensing 2005). So the Pb-Pb isochron
ages are mostly older (or equal to) the Sm-Nd isochron age of the St Séverin (LL6) chondrite (table 6 and fig. 13), but this is not the case with the Bjurböle (L4) chondrite (table 4 and fig. 11) and
the Richardton (H5) chondrite (table 2 and fig. 9), where some Sm-Nd isochron ages are older than the Pb-Pb isochron ages. So again the effect of the half-lives may result in the occasional equality or
reversal in the pattern of their isochron ages.

It is therefore fairly obvious that there are no clear and consistent patterns in these meteorite isochron ages comparable to the patterns of isochron ages obtained in the RATE study. However, there
is a major difference between the RATE study and these studies on meteorites, in that the RATE study investigated earth rocks that yielded isochron ages of less than 3 Ga, whereas these meteorites come
from elsewhere in the solar system and generally yield 4–5 Ga ages. So the origin of these meteorites could well have a major bearing on the radioisotope ages they yield, as initially discussed by Snelling
(2014).

The Origin of Meteorites from Asteroids

There is unanimity among astronomers and planetary geologists that most meteorites come from asteroids, which are primarily orbiting the Sun in the asteroid belt between Mars and Jupiter (Libourel and
Corrigan 2014). There is also unanimity among conventional scientists that the asteroids represent leftover precursors to the terrestrial planets (Mercury-Mars) (Michel 2014). They postulate that about
4.56 billion years ago the early solar system consisted of a rotating disk of gas and dust, called the protoplanetary disk, revolving around the sun. Planets then supposedly formed from that disk, and
different populations of small bodies, in particular the main belt asteroids between the orbits of Mars and Jupiter, survived as remnants of that era.

According to current conventional models, the asteroid belt that remained at the end of the planet-forming processes was probably very different from the current main belt, perhaps containing an earth
mass or more of material in planetary embryos with masses similar to the Moon or Mars, as well as tens, hundreds, or thousands of times more bodies like the asteroid 4 Vesta and the dwarf planet 1 Ceres
than are present in the main belt today (Michel 2014). Throughout its history the asteroid belt appears to have been shaped by collisional processes, such as cratering, disruption, and the generation
of new asteroids as collisional fragments. The net result is that the total mass of the main asteroid belt today is only about 4% of the Moon’s mass, or less than 1/1000th of the Earth’s mass (Libourel
and Corrigan 2014). So it would appear that the asteroid belt has been significantly depleted of asteroids since its early history.

Orbital resonances, when two bodies have orbital periods that are a simple integer ratio of each other, may lead to destabilization of the orbits of small bodies (Libourel and Corrigan 2014). Within
the main asteroid belt, objects that have orbital periods in resonance with the orbital period of Jupiter are gradually ejected into different, random orbits, leading to the removal of asteroids from
regions within the main asteroid belt that are now empty. Another important resonance is that between asteroids and Saturn, which has formed the inner boundary of the main asteroid belt, and which is
responsible for delivering asteroids into planet-crossing orbits. Once asteroids become Mars-crossers they are usually ejected from the main asteroid belt due to close encounters with Mars’ gravitational
field. If Mars-crossing asteroids fail to interact with Mars, then their orbital semi-major axes are gradually reduced and they become Near Earth Asteroids (NEAs).

Asteroids that are nudged by the gravitational attraction of nearby planets or have significant inclination and eccentricity may collide with other bodies traveling along different orbits (Libourel and
Corrigan 2014). Even if the current impact probability appears low, collisions between asteroids are not rare, and do not appear to have been rare in the past. Depending on the relative impact velocity
between the bodies and on their sizes, collisions result in 1) fragmentation of a parent asteroid into several large pieces, and/or 2) the formation of fine, micron-sized asteroidal dust. A collision
between large asteroids brings into play both fragmentation and gravitation (Michel 2014). The asteroids are partially to totally shattered, and subsequent gravitational attraction between fragments leads
to reaccumulation, which finally forms an entire family of large and small objects (new asteroids). Accordingly, most of the smaller asteroids are thought to be piles of rubble held together loosely by
gravity (Michel and Richardson 2013; Tsuchiyama 2014). The largest asteroids, those larger than 125 km (200 mi) in diameter, however, are probably primordial objects that have never been disrupted (Asphaug
2009; Michel 2014). Asteroids are therefore currently thought to have been quite mobile within the main belt. Due to asteroid collisions and other effects, main belt asteroids migrate, passing through
the orbital resonances to end up crossing the orbits of Mars, Earth, Venus, and even Mercury (Libourel and Corrigan 2014). NEAs do not have stable orbits, so they have relatively short lifetimes. Once
the orbits of asteroids whose diameters exceed 100–150 m (330–490 ft) are within 7.5 million km (4.7 million mi) of the earth’s orbit, there is a greater possibility of them colliding with the earth and
impacting its surface. By definition, meteors are asteroids that enter the earth’s atmosphere. Due to their high entry velocity (several kilometers per second) they are heated to high temperatures as
they are slowed by the atmosphere. This produces visible paths, and the meteors are then known as fireballs or shooting stars. If the meteors survive their plunge through the atmosphere and land on the
earth’s surface, they are classified as meteorites.

From these orbital and dynamical arguments, it is believed that most meteorites have indeed come from the asteroid belt and therefore are samples of asteroidal materials (Cloutis, Binzel, and Gaffey
2014; Libourel and Corrigan 2014). However, linking meteorites to their parent asteroids is a complicated issue. There is a photographic technique that has been used to get estimates of the orbital parameters
(approximately) of meteors before they make contact with earth’s atmosphere. Two cameras have to have synchronized shutters and photograph the object before it makes contact with the atmosphere. This
has been done for a few cases of meteors and the orbital elements suggest the objects did come from the asteroid region. So there are some cases where this has been done and then fragments of the photographed
objects were found, which has established good indications of meteorites coming from asteroids. Furthermore, there have been a multitude of methods used to investigate asteroids, such as earth-based radar
imaging, optical and radar polarimetry, thermal-infrared observations, reflectance spectroscopy, and thermal emission spectroscopy, but only the availability of meteorites of known provenance has enabled
additional confirmation of asteroid-meteorite links. Two recent examples confirming the asteroid-meteorite link are relevant to the H, L, LL, and E chondrites in this study.

On October 6, 2008, the small, ~4 m (13 ft) wide asteroid 2008 TC3 was discovered and predicted to hit the earth within ~19 hours (Goodrich, Bischoff, and O’Brien 2014). Early morning, October 7, 2008,
eyewitnesses saw the fireball that resulted when the asteroid hit the earth’s atmosphere above the Nubian Desert of northern Sudan, Africa. A few seconds later, at ~37 km (23 mi) above the earth, the
asteroid was shattered in the atmosphere by dynamic ram pressures in a series of explosions into fragments. Approximately 700 cm-sized (275 in-sized) fragments were subsequently recovered and constitute
what became known as the Almahata Sitta meteorite. Study of their physical, chemical, and mineralogical properties has revealed that the fragments are remarkably heterogeneous. The most abundant samples
are ureilitic lithologies (see fig. 1— URE among the Primitive Achondrites) with various olivine/pyroxene ratios, mineral compositions and grain sizes (Bischoff et al. 2010; Goodrich, Bischoff, and O’Brien
2014). Among the chondritic samples, enstatite (E) chondrites are the most abundant, including both E chondrite subgroups (EL and EH), though the EL subgroup dominates, with representatives of the various
petrologic types (EL3, EL4, EL5, and EL6), which are indistinguishable from previously known E chondrites. So far, several L and H group ordinary (O) chondrites have also been analysed. It has been concluded
that the 2008 TC3 asteroid was not solid rock, but consisted mostly of fine-grained, highly porous matrix material, weakly cementing a small fraction of isolated, centimeter-sized fragments of denser
rocks that became the fallen meteorite.

In June 2010 the Japanese spacecraft Hayabusa successfully returned to earth with fine particles collected in September 2005 from the surface of Near Earth Asteroid 25143 Itokawa (Nakamura et al. 2011;
Tsuchiyama 2014). Measuring 30–180 μm (0.0011–0.007 in) in diameter, initial analyses of the mineralogy, micropetrology, and elemental and isotopic compositions of the returned regolith particles from
asteroid Itokawa indicate that these dust particles are identical to thermally metamorphosed LL chondrites, particularly the LL5 and LL6 ordinary chondrites, such as Olivenza and St. Séverin (respectively)
in this study.

A Biblical Perspective

Faulkner (1999) suggested that when God created the other planets and satellites on Day Four of the Creation Week He may have formed them from material He had already created in His creative act
of Genesis 1:1. In further developing this proposal, Faulkner (2013) pointed out that the Hebrew word ‘āśâ meaning “to do” and “to make” is used specifically of the creation of the astronomical bodies in
Genesis 1:16, rather than the Hebrew word bārā’ meaning “to create” as used in Genesis 1:1 in reference to the creation of the universe generally. Indeed, the Hebrew word bārā’ appears only
with God as its agent (cf. Koehler and Baumgartner 2001, p. 153). Similarly, the Hebrew word ‘āśâ is used in Genesis 1:26 when God took already-existing material, which in Genesis 2:7 we are told
was “the dust of the ground”, to make man’s body, before breathing “into his nostrils the breath of life” to make man “a living soul” (Genesis 2:7). Faulkner (2013) goes on to say:

Granted, such is not always the intended meaning, even with respect to the astronomical bodies (for example, compare Genesis 1:1 with 2 Kings 19:15; Isaiah 37:16, 66:22; Jeremiah 32:17). However,
the use of ‘āśâ in the Day Four creation record apart from any contextual clues to suggest that it must bear the sense of creation out of nothing suggests that there is a distinct possibility that
the making of the astronomical bodies was instead a matter of fashioning them from material previously created on Day One. Just as the description of the earth in Genesis 1:2 is of something unfinished
that God returned (to) over the next several days to shape and prepare, perhaps the matter that would become the astronomical bodies was created on Day One but was shaped on Day Four. (p. 298, emphasis
his)

Furthermore, as Snelling (2014) pointed out, though Jesus took already-existing water to make it into wine at the wedding feast in Cana (John 2:1–11), it was nonetheless a similar act
of creation, because He was taking water molecules and adding to them carbon atoms as He instantaneously fashioned it all into the complex organic molecules of wine.

Therefore, it seems entirely possible to read Genesis 1:16 as saying God used already-existing “primordial material” which He had created out of nothing at the beginning of Day One
of the Creation Week (Genesis 1:1) to then fashion it on Day Four into the other planets, their satellites and the stars. Snelling (2014) thus argued that the asteroids could similarly
be regarded as Day One primordial material left over from the making of the other planets and their satellites in the solar system on Day Four. Since most meteorites are believed to have been derived
from asteroids via collisions between them breaking off fragments that then hurtled towards the earth, and this asteroid-meteorite link has now been confirmed by observational examples, then this would
imply the meteorites could represent samples of this same Day One “primordial material.”

Similarly, this would have to also mean that at the beginning of Day One the earth was also fashioned out of the same “primordial material.” Thus Snelling (2014) suggested that the 4.56–4.57 Ga Pb isotopic
composition of the well-studied Allende CV3 carbonaceous chondrite meteorite and the bulk earth, as plotted on the age of the earth isochron known as the geochron (Patterson 1956), may represent a geochemical
signature from this “primordial material” created by God “in the beginning.” The results of this study add to that possibility, since several of the well-studied meteorites reported here—Richardton (H5),
St. Marguerite (H4), Bardwell (L4), Bjurböle (L5), and St. Séverin (LL6) in particular—clearly also have a 4.56–4.57 Ga Pb isotopic composition, supported by some other isotope systems. This same geochemical
signature would be expected if the asteroids from which these meteorites came also represent the same Day One “primordial material” out of which the earth, the other planets, their satellites and the
asteroids were all made.

This raises the obvious question about another aspect of the radioisotope dating technique, also discussed by Snelling (2014). The evidence of past accelerated radioisotope decay (non-constant radioisotope
decay rates), that is, the inconsistent radioisotope age data in some Precambrian earth rocks (Vardiman, Snelling, and Chaffin 2005), would appear to negate the assumption of constant decay rates that
enables the radioisotope “clocks” to be “reading” 4.56–4.57 Ga for the supposed elapsed real time since the formation of the asteroids, the meteorites derived from them, and the earth. However, another
assumption necessary for these radioisotope “clocks” to work is that all the daughter isotopes were only derived by radioisotope decay from the parent isotopes. But what if God made all the isotopes at
the beginning in the “primordial material,” including isotopes that subsequently also formed by radioisotope decay as daughter isotopes from parent isotopes? In other words, when God made the “primordial
material” did He include in it 206Pb, 207Pb, and 208Pb atoms along with 238U, 235U, and 232Th atoms? It may be reasonable to posit that He did, given that when created the “primordial material” likely
had to have some initial isotopic ratios. Even the conventional scientific community has assumed the initial material of the solar system had the “primeval” Pb isotopic ratios as measured in the troilite
(iron sulfide) in the Canyon Diablo iron meteorite (Faure and Mensing 2005). So if He did, then the Pb isotopes we measure today are not all the product of radioisotope decay, due to some being created
in place in the beginning, and they therefore cannot be measuring the elapsed real time since God created the earth and the universe at the beginning only about 6000 real-time years ago.

Following from this is another consideration. How many atoms of each of the Pb isotopes did God create in the “primordial material”? And if the 4.56–4.57 Ga “age” for these meteorites is a geochemical
signature of the “primordial material” God created with some of each of the Pb isotopes we measure today already in it, then how many of the atoms of the measured-today Pb isotopes are due to past accelerated
radioisotope decay? Is it most of them, or only some of them? So far we don’t know. What we do know is that here on the earth we don’t find rocks that still have the 4.56–4.57 Ga Pb isotopic signature
in them, though most rocks that date back to the continental foundations laid down during Creation Week, the lower Precambrian rocks, still contain various large amounts of Pb isotopes in them and therefore
yield an array of multi-Ga “ages”. Significantly, the earth sample that plotted on the geochron (Patterson 1956) was a modern ocean sediment sample whose Pb isotopic signature had been acquired by mixing
and integration from many earth rocks over much of the time of the earth’s history. This may point to a possible third additional process responsible for the Pb isotopic compositions in earth rocks, namely,
inheritance of the primordial geochemical signature and then mixing of it with the isotopes generated by subsequent radioactive decay in the earth’s mantle and crust since the creation of the original
earth on Day One of the Creation Week. This has been previously proposed by Snelling (2000, 2005) as primarily occurring during the catastrophic geologic processes of the Day Three Upheaval when the dry
land was formed, and then again during the Flood (Snelling 2009). And as part of this mixing process the primordial geochemical signature could also have been diluted by the addition of parent isotope
atoms, thus making the resultant rocks appear to progressively “date” younger.

As Snelling (2014) also observed, the Pb-Pb radioisotope dating technique has proven precise in measuring the apparent age of meteorites such as the Allende CV3 carbonaceous chondrites and several of
the ordinary (O) chondrites (H, L, and LL) reported in this study. The other radioisotope dating techniques are more variable in their reliability, most of those isotopic systems (K-Ar, Rb-Sr, U-Pb, Th-Pb,
Sm-Nd, and Re-Os) being apparently subject to disturbance by processes and conditions subsequent to the formation of the asteroids from the Day One “primordial material.” Such processes meteorites were
subjected to after the asteroids were formed on Day Four include space weathering (Cloutis, Binzel, and Gaffey 2014), fragmentation and reassembly of their parent asteroids (Michel 2014), reheating and
pressure during passage through the earth’s atmosphere, pressures from disintegration into fragments in the earth’s atmosphere and then from impacting the earth’s surface, and weathering while lying on
the earth’s surface before collection for study. However, such post Day One creation disturbances of the radioisotope systems were largely within the closed confines of the parent asteroids or the resultant
meteorites. In contrast, there were greater opportunities for much larger disturbances, additions and subtractions in earth rocks, because they have been subjected to the cataclysmic geologic processes
of the Day Three Upheaval and then the Flood. For example, the melting of large batches of rocks both in the mantle and crust formed magmas in which the isotopes were mixed, homogenized, and the radioisotope
“clocks” reset before crystallization and cooling formed new rocks with new isotope ratios distinct from those in the original rocks. It will thus take a lot more research on many earth rocks to unravel
and elucidate the proportions of isotopes from each of these major contributing factors and processes—inheritance of the primordial geochemical signature, accelerated radioisotope decay, and mixing in
the mantle and crust—to the “dates” measured today by using these radioisotope systems.

The resultant conclusion from all these considerations, based on the assumptions made, is that the 4.56–4.57 Ga “ages” for the Richardton (H5), St. Marguerite (H4), Bardwell (L5), Bjurböle (L4), and
St. Séverin (LL6) ordinary chondrite meteorites obtained by Pb-Pb radioisotope isochron and model age dating of various constituent minerals and fractions (for example, Amelin, Ghosh, and Rotenberg 2005;
Bouvier et al. 2007; Göpel, Manhès, and Allègre 1994; Kleine et al. 2008; Rotenberg and Amelin 2001 respectively) are likely not their true real-time ages. The assumptions on which the radioisotope dating
methods are based are simply unprovable, and in the light of the possibility of an inherited primordial geochemical signature, and the evidence for both possible past accelerated radioisotope decay and
mixing of isotopes in earth rocks, these assumptions are unreasonable. However, we are still left without a coherent explanation of what these radioisotope compositions in both meteorites and earth rocks
really represent and mean within our biblical young-age creation-Flood framework for earth and universe history. We have some possible clues already, and a clearer picture may yet emerge from continued
investigations now in progress, for example, of the radioisotope dating of more meteorites, and also of many more earth rocks from all levels of the geologic record.

Conclusions

After decades of numerous careful radioisotope dating investigations of ordinary (O) chondrite meteorites (H, L, and LL groups) and enstatite (E) chondrite meteorites their Pb-Pb isochron age of 4.55–4.57
Ga has been well established. This date for these chondrite meteorites is supported for some of them by a strong clustering of their Pb-Pb isochron and model ages in the 4.55–4.57 Ga range, as well as
being confirmed by both isochron and model age results via the U-Pb method, and to a lesser extent, by the Ar-Ar, Rb-Sr, Re-Os, and Sm-Nd methods. The Hf-W, Mn-Cr, and I-Xe methods are all calibrated
against the Pb-Pb isochron method, so their results are not objectively independent. Thus the Pb-Pb isochron dating method stands supreme as the ultimate, most precise tool for determining the ages of
the chondrite meteorites.

There are only two other discernible patterns in the isochron and model ages for these O and E chondrites, apart from scatter of the U-Pb, Th-Pb, Rb-Sr, and Ar-Ar model ages particularly. These chondrite
ages do not follow the systematic pattern found in Grand Canyon Precambrian rock units during the RATE project. The α-decay ages are not always older than the β-decay ages for particular meteorites, and
among the β-decayers the ages are not always older according to the increasing heaviness of the atomic weights of the parent radioisotopes, but may have also been modified according to the lengths of
their half-lives. Thus there appears to be no consistent evidence in these O and E chondrite meteorites similar to the evidence found in earth rocks of past accelerated radioisotope decay.

Any explanation for the 4.55–4.57 Ga age for these O and E chondrite meteorites needs to consider the origin of meteorites. Most meteorites appear to be fragments derived from asteroids via collisions,
but even in the naturalistic paradigm the asteroids, and thus the meteorites, are regarded as “primordial material” left over from the formation of the solar system. Similarly, the Hebrew text of Genesis
could suggest God made “primordial material” on Day One of the Creation Week from which He made the earth on Day One and the non-earth portion of the solar system on Day Four, so today’s measured radioisotope
compositions of these O and E chondrite meteorites may reflect a geochemical signature of that “primordial material,” which included atoms of all elemental isotopes created by God. Therefore if some of
the daughter isotopes were thus “inherited” by these O and E chondrite meteorites when they were formed from that “primordial material,” and the parent isotopes in the meteorite were also subject to some
subsequent accelerated radioisotope decay, then the 4.55–4.57 Ga Pb-Pb isochron “age” for these O and E chondrite meteorites cannot be their true real-time age, which according to the biblical paradigm
is only about 6000 real-time years.

However, these conclusions and the suggested explanation can at best be regarded as tentative and interim while their confirmation or adjustment awaits the examination of more radioisotope dating data
from many more meteorites. Furthermore, further extensive studies of the radioisotope dating of many more earth rocks from all levels within the whole geologic record are required to attempt to systematize
the proportions of isotopes in each radioisotope dating system measured today that are due to inheritance from the “primordial material,” past accelerated radioisotope decay, and mixing, additions and
subtractions in the earth’s mantle and crust through earth history, particularly during the Day Three Upheaval and then subsequently during the Flood. Such studies are already in progress.

Acknowledgments

The invaluable help of my research assistant Lee Anderson, Jr., in compiling these radioisotope dating data into the tables and then plotting the data in the color coded age versus frequency histogram diagrams is acknowledged.

Snelling, A. A. 2000. Geochemical processes in the mantle and crust. In Radioisotopes and the age of the earth: A young-earth creationist research initiative, ed. L. Vardiman, A. A. Snelling, and E. F. Chaffin, pp. 123–304. El Cajon, California: Institute for Creation Research; St. Joseph, Missouri: Creation Research Society.

Snelling, A. A. 2005. Isochron discordances and the role of inheritance and mixing of radioisotopes in the mantle and crust. In Radioisotopes and the age of the earth: Results of a young-earth creationist research initiative, ed. L. Vardiman, A. A. Snelling, and E. F. Chaffin, pp. 393–524. El Cajon, California: Institute for Creation Research; Chino Valley, Arizona: Creation Research Society.

Answers Research Journal

2014 Volume 7

Cutting-edge creation research. Free. Answers Research Journal (ARJ) is a professional, peer-reviewed technical journal for the publication of interdisciplinary scientific and other relevant research from the perspective of the recent Creation and the global Flood within a biblical framework.